While reduction in power consumption is requested in portable wireless device, increase in antenna gain is requested in order to achieve remote distance communication with low power. As one of means for attaining increase in antenna gain, there is an array antenna in which a plurality of antennas are arrayed so that the directivity can be fixed to one direction by control of excitation phases of the respective antennas.
Of array antennas, an array antenna whose directivity is fixed to the array direction is called an end-fire array antenna. A Yagi array antenna which uses dipole type radiation elements, a reflector and a director is known as one of end-fire array antennas.
As to Yagi array antennas, for example, Patent Literature 1 discloses a Yagi array antenna. FIG. 10 is a view showing the configuration of the Yagi array antenna disclosed in Patent Literature 1. In the Yagi array antenna shown in FIG. 10, dipoles 901 and 902 serving as radiation elements and microstrip lines 903 and 904 feeding power to the dipoles 901 and 902 are printed in a substrate 900 consisting of a dielectric substrate.
A director 905 and a reflector 906 are printed at a distance from the dipole 901 in a first surface of the two surfaces of the substrate 900. A plane Yagi array antenna is comprised by the director 905, the reflector 906 and the dipoles 901 and 902. A tapered balun 907 connected to the micro-strip line 904 disposed in a second surface of the substrate 900 and a ground plane 908 connected to the tapered balun line 907 are printed in the second surface.